UV-induced mortality of zoea I larvae of brown shrimp Crangon crangon (Linnaeus, 1758)

Zoea I larvae of the brown shrimp Crangon crangon (Decapoda)were exposed to varying levels of UV radiation in a sunshinesimulator. ‘Short-term exposures’ (0–8 h)were used to determine the highest UV dose with no significanteffect (NOEC; defined by limit of detection) and the lethaldose of 10 and 50% mortality (LD₁₀ and LD₅₀). Crangon crangonshowed a relatively high sensitivity to UVB radiation (NOEC= 10 kJ m^–2, LD₁₀ = 15 kJ m^–2, LD₅₀ = 24 kJ m^–2)compared to other crust-acean species. LD values (1997–1998)showed no adaptation to seasonal light regimes. ‘Long-termexposures’ (0–10 days) were carried out to assessthe range where the ‘law of reciprocity’ is valid.The larvae were exposed to UV levels of 0.2, 0.4 and 0.7 J m^–2for appropriate time intervals, always cumulating in a sublethaldose of 5 kJ m^–2 day^–1. Results reflect a possiblethreshold (0.2–0.4 J m^–2 UVB) in the effect of thedifferent UVB doses used; thus, a proportional relationshipof intensity and exposure time can only be shown at UVB levelsabove this threshold intensity.     

The light-harvesting system of Euglena gracilis during the cell cycle

The apoproteins of the light-harvesting chlorophyll-protein complexes LHCI and CP29 (apparent molecular weights of 27 kDa and 29 kDa, respectively) of Euglena gracilis were identified immunologically. Both complexes are present in the thylakoids of autotrophically cultured Euglena cells during the whole cell cycle. The relative amount of each apoprotein tends to increase towards the end of the cell cycle. The light-harvesting chlorophyll-protein complex of photosystem II, LHCII, of E. gracilis contains chlorophyll a, chlorophyll b, neoxanthin, diadinoxanthin and beta-carotene. Its chlorophyll a/b ratio is about 1.7 during the whole cell cycle. About 9 h after cell division the ratio of diadinoxanthin to chlorophyll a is doubled for a time of 3–4 h. The relevance of this increase during one developmental stage is discussed in relation to the insertion and-or assembly of newly synthesized LHCII.Abbreviations LHCP light-harvesting chlorophyll-protein complex - PS photosystem This research was partly supported by the Deutsche Forschungsge meinschaft.     

Selective decomposition of either enantiomer or aspartic acid irradiated with60Co-γ-rays in the mixed aqueous solution with D- or L-alanine

Aqueous solutions of various amino acids were irradiated with⁶⁰Co--rays, and subsequently the remaining amino acids were analyzed using HPLC. The D₃₇ for the 1 mM glycine and alanine solutions were 1.95×10⁴ and 1.48×10⁴ Gy, respectively. However, when the mixed solutions of glycine and alanine (each in 0.5 mM) were irradiated under the identical condition, the D₃₇ for the glycine decomposition increased to 3.56×10⁴ Gy, while that for alanine decreased to 0.65×10⁴ Gy. A similar phenomenon was observed also in the case of the mixed solutions of aspartic acid and alanine. Namely, aspartic acid was protected from the attack of radiation by the presence of alanine in the solutions. The most interesting finding in this combination experiment is that, when D,L-aspartic acid was irradiated in the presence of L-alanine, the radiation-sensitivity of L-aspartic acid decreased selectively and vice versa. Namely, the asymmetric field induced in the solutions by adding D- or L-alanine might affect the radiodecomposition rate of either aspartic acid. Addition of glycine to D,L-aspartic acid did not bring about the asymmetric decomposition. It seems that some interaction between these amino acid molecules resulted in this effect.     

High frequency callus formation from maize protoplasts

Summary A solid feeder layer technique was developed to improve callus formation of Black Mexican Sweet maize (Zea mays L.) suspension culture protoplasts. Protoplasts were plated in 0.2 ml liquid media onto a cellulose nitrate filter on top of agarose-solidified media in which Black Mexican Sweet suspension feeder cells were embedded. Callus colony formation frequencies exceeding 10% of the plated protoplasts were obtained for densities of 10³–10⁵ protoplasts/ 0.2 ml, which was 100- to 1,000-fold higher than colony formation frequencies obtained for conventional protoplast plating methods such as liquid culture or embedding in agarose media. Compared with conventional methods, the feeder layer method gave higher colony formation frequencies for three independently maintained Black Mexican Sweet suspension lines. Differences among the three lines indicated that colony formation frequencies might also be influenced by the suspension culture maintenance regime and length of time on different 2,4-dichlorophenoxyacetic acid concentrations. The callus colony formation frequency reported is an essential prerequesite for recovering rare mutants or genetically transformed maize protoplasts.     

Nuclear magnetic resonance studies on oligo-deoxyribonucleotides containing thedam methylation site GATC. Adenine methylation of d(GGATCC) does not change the helix geometry

We have studied the conformation of two hexanucleotides d(GGATCC) and d(GGm⁶ATCC) using proton nuclear magnetic resonance. Nuclear Overhauser effect measurements show that d(GGATCC) assumes a normal right handed B helix. The single and double strand resonances are in fast exchange on a proton nuclear magnetic resonance time scale. For d(GGm⁶ATCC), up to the Tm separate resonances are observed for each state, indicating slow exchange, though above the Tm it becomes more rapid. The orientation of the adenosine methyl-amino group, preferentiallycis to N¹, hinders base pair formation.The connectivities of the resonances of the two states were established by saturation transfer experiments. At 0°C irradiation of the m⁶ A-T imino proton gives an nuclear Overhauser effect to AH² showing that base pairing is Watson-Crick. Intra and interresidue nuclear Overhauser effects starting from the 3′ terminus show that the helix is right handed and in the B-form.The results on the two oligomers demonstrate that adenosine methylation induces little or no change in the conformation of the helix, but reduces the Tm from 45° to 32°C and slows the opening and closing of the m₆A.T base pair by a factor of about 100.     

Production of an antiserum against cyclic nucleotide phosphodiesterase and its use for the immunocytochemical demonstration of this enzyme in rat cerebellum

Summary A procedure for the separation of cyclic AMP phosphodiesterase from a commercially available preparation and for raising antibodies against this enzyme in rabbits is described. An antiserum thus obtained was used for the immunocytochemical detection of cyclic nucleotide phosphodiesterase in rat cerebellum. The molecular layer, the granular layer and the cerebellar white matter exhibited different degrees of immunoreactivity. Only a few cell bodies (possibly glial cells) were stained. Most of the antigenic sites were present in the neuropil of the molecular layer and around Purkinje cells. Cerebellar glomeruli, sites of synaptic interactions between mossy fibres, Golgi cells and granule cells, were also stained by this antiserum. Control reactions using preimmune serum were consistently negative.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday.     

The Molecular Analysis of the Light Adaptation Reactions in the Yellow-green Alga Pleurochloris meiringensis (Xanthophyceae)

The xanthophycean alga Pleurochloris meiringensis was homocontinuously cultured under high light (16 W/m²) and low light (2 W/m²) conditions. In low light cells, the chlorophyll a content and the dry weight on per cell basis is increased, the maximal photosynthetic capacity per chlorophyll is decreased. The content of chlorophyll c, vaucheriaxanthin-ester and heteroxanthin is similar in both cultures, whereas the content of diadinoxanthin and ß-carotene is twice as high in high light cultures. High light cells contain more photosystem I and cytochrome f per chlorophyll than low light cells, whereas the Q_B content is found to be unchanged. Therefore, the ratio reaction center II/reaction center I is twofold higher in low light cells than in high light ones. The regulation of energy distribution between the photosystems is examined by fluorescence emission spectra at 77 K scanned after different preillumination of the cells. No wavelength dependent state I/state II transition can be detected. However, P. meiringensis regulates the energy distribution in response to light intensity: The higher the irradiance of preillumination, the higher the energy transfer to photosystem I. The sensitivity of the regulation to light intensity is increased in low light cells.     

Differential responsiveness of human neutrophils to the autocrine actions of 1-O-alkyl-homologs and 1-acyl analogs of platelet-activating factor.

The phlogistic actions of six molecular species of platelet-activating factor (PAF) (1-O-alkyl-PAF homologs, 16:0-, 18:0- and 18:1-alkyl-PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC) and their respective 1-acyl-PAF analog counterparts, 16:0-, 18:0- and 18:1-acyl-PAF, 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (AGPC)) were assessed relative to five human neutrophilic polymorphonuclear leukocyte (PMN) functional responses: 1) lysosomal enzyme secretion; 2) specific desensitization to 16:0-AGEPC-induced lysosomal enzyme secretion; 3) O2- production; 4) chemotaxis; and 5) priming for enhanced O2- production. With respect to inducing lysozyme secretion, 18:0-AGEPC was 30- and 75-fold less potent than 16:0-AGEPC and 18:1-AGEPC, respectively, and was 25- and 40-fold less potent for inducing beta-glucuronidase secretion. 18:0-AGEPC was also 10-fold less active than 18:1- and 16:0-AGEPC for inducing O2- production. Thus, the rank order of potency of the alkyl-PAF homologs for inducing both lysosomal enzyme secretion and O2- production was 18:1- greater than or equal to 16:0- much greater than 18:0-AGEPC. In contrast, these three alkyl-PAF homologs had the same potency for desensitizing PMN to subsequent 16:0-AGEPC-induced lysosomal enzyme secretion and for priming PMN for augmented O2- production in response to FMLP or human recombinant C5a. Paradoxically, however, the rank order of potency of the alkyl-PAF homologs for effecting PMN chemotaxis was 18:0- greater than 18:1- much greater than 16:0-AGEPC. At concentrations as high as 1.0 microM, the acyl-PAF analogs did not initiate PMN lysosomal enzyme secretion, O2- production, or chemotaxis. However, the acyl-PAF analogs induced partial PMN desensitization to 16:0-AGEPC. A novel finding of potential (patho)-physiologic significance was the ability of acyl-PAF at nM concentrations to prime PMN for significantly enhanced O2- production after stimulation with FMLP or human recombinant C5a. The priming action of acyl-PAF was due to an increase in the rate as opposed to a prolongation of O2- production. The differing rank orders of potency of the alkyl-PAF homologs and acyl-PAF analogs for stimulating several physiologic responses of the same target cell, the human PMN, support the premise that there may be more than one PAF receptor subtype on the PMN and/or that differences in the biophysical properties of the various molecular species of PAF modulate their interaction with PAF receptor(s) linked to stimulus-response coupling.     

ph-Dependent hydrophobicity profile of hemagglutinin of influenza virus and its possible relevance in virus fusion

The hydropathy profile of hemagglutinin (HA) subunits HA1 and HA2 of influenza virus X31 and A/PR 8/34 is analyzed at different pH. At neutral pH (7.4) pronounced hydrophobic sequences of HA correspond to the N-terminus and the transmembrane spanning sequence of HA2. At pH 5.0 where influenza virus is known to fuse with biological membranes several hydrophobic sequences in the ectodomain exist which are comparable in both the hydrophobicity and length of the N-terminus of HA2. It is suggested that these hydrophobic stretches are important for the fusion complex, in addition to the N-terminal site of HA2.Abbreviations HA hemagglutinin - NHA2 N-terminus of HA2